Robust Gain Allocation against Phase Uncertainty at the Relays for Multiuser Cooperative Networks


Celal Esli and Armin Wittneben


Asilomar Conference on Signals, Systems and Computers, Oct. 2008.

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We consider a coherent multi-user relaying network, where multiple source/destination pairs communicate concurrently over the same physical channel and several amplifyand- forward relays assist them. It has been shown recently that distributed phase synchronization can be avoided in coherent forwarding schemes. However, the channel estimates at the relays used for gain allocation, so as the signal-to-noise plus interference ratios at the destinations, are severely affected by the random phase uncertainty at the local oscillators. We propose a robust design for relay gain allocation based on semidefinite programming, where the phase uncertainties at the relays are bounded within a defined range determined according to the desired probability of assurance. The robust design has shown to provide a substantial gain over the non-robust approach.

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